Construction of space-time statistical models for seismicity and stress changes

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(1) Increased probability of large earthquakes near aftershock reions with relative quiescence By appiyin the ETAS model, aftershock sequences in Japau during the last century are descriminated whether they decayed normally or changed to become quiet relative to the model Then it is shown that the reiative quiescence is a helpful factor to forecast whether or not a large event is more likely to follow within 6 years in the neighborhood (say, within a distance of 200km) of the initial event.(2) Bayesian hierchical spaee-time ETAS model and detection of relative quiescenceA space-time point-process model is specified in which earthquake intenshy is mqdeiled as a functlon of previous activity where the parameters are further considered to be functions ofspatial locations (but not time) represented by tinear interpolation over a tessellation based on observed locations of earthquakes. We detect the temporal deviation of the actual seisrnicity rate from that of the modeiled occurrence rate. … More Thus we showed a number of zones where temporal deviation from the fitted model, with quiet periods, occurred before latge earthquakes.(3) Qualitative study on the relation between the relative quiescence and precursory aseismic slip We have shown a number of examples such that, assuming aseismic siip within a fault of forthcoming large event, subregions where aftershocks indicate the relative qLLiescence correspond to the shadow of the Coulomb stress changes.(2) Other results(A) The maximum likelihood procedure for the Vere-Jones' trigger model is impiemeted to for expioratory analysis of earthquake clusters. (B)'The stochastic declustering aigorithm is proposed and demonstrated by using the space-time ETAS modeis. (C) We demonstrated statistical confirmation of a relationship between excitation of the low-frequency electric fietd and magnitude M>=4 earthquakes in a 300km radius region around Beij ing, by making use of the Lin-Lin point process model. (D) Aftershock sequence of acoustic emissions is successfully modelled to detect the causal relationship with earth-tide stress. Less